Electrical service providers such as electrical utilities employ electricity meters to monitor energy consumption by customers (or other entities). Electricity meters track the amount of energy consumed by a load (e.g. the customer), typically measured in kilowatt-hours (“kwh”), at each customer's facility. The service provider uses the consumption information primarily for billing, but also for resource allocation planning and other purposes.
Electrical power is transmitted and delivered to load in many forms. For example, electrical power may be delivered as polyphase wye-connected or delta-connected power or as single phase power. Such various forms are known as service types. Different standard electricity meter types, known as meter forms, are used to measure the power consumption for the various service types. The commonly used meter forms in the United States include those designated as 2S, 3S, 5S, 45S, 6S, 36S, 9S, 16S, 12S and 25S meter forms, which are well known in the art.
While utility electrical power systems are designed to deliver a consistent service voltage level (e.g. 240 volts AC), system strain and other factors can result in temporary variances in service voltage. For example, it is possible for service voltage to all or parts of a utility service area to surge (exceed the nominal or expected voltage) by 20% or more. Similarly, in so-called brown out situations, the service voltage can be reduced (i.e. a voltage sag).
A problem with service voltage sags and swells is that they can create strain on end-user equipment and systems that are designed to work with the nominal service voltage. For example, the motors of an HVAC system may overheat and be damaged if the service voltage is too low, and or an entertainment system may be damaged by too high of a service voltage.
There is a need therefore, for protecting user equipment from potentially damaging power sags and/or power surges.